An adjustment apparatus is known from EP 0 913 848 A2.
A switching device is used for connecting a circuit to a power supply system and for manual and automatic disconnection of the circuit from the power supply system when the current exceeds a predetermined value. Thus, for example, a line circuit breaker is used for protecting lines in installations and systems from overloading and short-circuits. In a power supply system in which disconnection is provided by overcurrent protective devices, a switching device such as this additionally prevents the existence of high direct contact voltages in the event of a fault.
When the switching device or circuit breaker is switched on, an energy store, for example a spring, is loaded as part of a mechanical switching mechanism. This energy is released during the tripping process, and operates the switch. In this case, the switching device has a thermal release in the form of a conventional bimetallic strip, which trips with a delay as a function of the overload time. The tripping process is initiated by thermal deformation of the bimetallic strip as a result of an overcurrent being passed through it.
This is done by a tripping lever, which is opposite the free end of the bimetallic strip, is at a distance from it, and is mechanically coupled to the switching mechanism, being acted on by the bimetallic strip. Thus, via this, the bimetallic strip unlatches the switching mechanism, while the energy store of the switching mechanism opens a moving contact, by lifting the latter off a fixed contact. Furthermore, the switching device normally additionally has a magnetic or electromagnetic release, which trips without any delay, for high surge currents and short-circuit currents.
The distance between the free end of the bimetallic strip and the tripping lever can be designed to be adjustable, and an adjusting screw is normally provided for this purpose. Switching devices in which an adjusting screw such as this is used to adjust the bimetallic strip are known, for example, from DE 1 904 731 A1, from EP 0 143 981 A1 and from EP 0 412 953 A3. However, the use of an adjusting screw is associated with corresponding production and manufacturing costs.
Furthermore, EP 0 913 848 A2 discloses a method for thermal calibration of the tripping mechanism of a switching device, and a corresponding tripping mechanism, in which the adjustment is carried out thermally by use of a laser.